Extiger,
Welcome aboard! Our track floats in a big raised bed garden. The entire bed has 6" of gravel on the top, the circumstance of a miscommunication with our contractor that worked to our advantage. This enabled a real “sandbox” approach that let us tinker with the track plan quite a bit. We chronicled quite a bit of the railroad’s first 2-3 years here Progress on the Triple O (http://cs.trains.com/grw/f/91/t/230077.aspx). It may prove helpful, as almost all of our stuff is old LGB, to include the track.
We, too, run track power. Over the years, we have used rail clamps to improve connectivity. We live in the tropics, though, so corrosion is a real thing! Also, we buy them in packets to spread the cost, deploying them in the worst places. Do note, depending on how many locos you have and how big your garden, it might be cheaper to convert to R/C with battery power. For us, with a large “heritage fleet” of old locos tied to family and friends, the cost tilted in favor of track power and “strategic rail clamping.”
As for zip ties…No clue. We tried those plastic track clips that come with LGB starter sets, and we found the ties started to split where those tracks connect. Thermal expansion? Torsional stresses from dogs / kids / me stepping on the track? Applicable to what you want to do at all? Not sure, but I’d try it on one section of track, let it sit for a couple months, and see what happens.
Battery power clearly eliminates any worry about how to hold the tracks togehter. You may also wish to consider how you plan to use you